prefer to use libfdk_aac for better audio quality

MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs

@@ -424,6 +424,11 @@ namespace MediaBrowser.Controller.MediaEncoding
 
             if (string.Equals(codec, "aac", StringComparison.OrdinalIgnoreCase))
             {
+                // Prefer to use libfdk_aac for better audio quality while using the custom build FFmpeg
+                if (_mediaEncoder.SupportsEncoder("libfdk_aac"))
+                {
+                    return "libfdk_aac";
+                }
                 return "aac -strict experimental";
             }
 

MediaBrowser.MediaEncoding/Encoder/EncoderValidator.cs

@@ -42,6 +42,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
             "libvpx",
             "libvpx-vp9",
             "aac",
+            "libfdk_aac",
             "libmp3lame",
             "libopus",
             "libvorbis",